springmvc后台基于@ModelAttribute获取表单提交的数据

package com.demo.model;

public class user {
  private String username;
  private String password;
  private int nsex;


  public String getUsername() {
    return username;
  }

  public void setUsername(String username) {
    this.username = username;
  }

  public String getPassword() {
    return password;
  }

  public void setPassword(String password) {
    this.password = password;
  }


  public void setNsex(int nsex) {
    this.nsex = nsex;
  }

  public int getNsex() {return nsex;}
}

<%--
 Created by IntelliJ IDEA.
 User: wym
 Date: 2019/10/8
 Time: 23:17
 To change this template use File | Settings | File Templates.
--%>
<%@ page language="java" cOntentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>



  
  



  用户名： 


  密码： 


  

package com.demo.controller;


import com.demo.model.user;
import com.demo.service.Userservice;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import javax.servlet.http.HttpSession;

@Controller
public class LoginController {
  @Autowired
  private Userservice userService;

  @RequestMapping(value="/login", method= RequestMethod.POST)
   public String hello(@ModelAttribute user u, HttpSession session){

      session.setAttribute("user", u);
    user user = userService.findbyname(u.getUsername());
    if(user == null)
      return "loginfail";
    else if(!user.getPassword().equals(u.getPassword()))
      return "falsepaswd";
    else
    return "helloworld";
  }


}

public String hello(@RequestParam(value="username") String A, @RequestParam(value="password") String B, HttpSession session){
    session.setAttribute("a", A);
    session.setAttribute("b", B);
    user user = userService.findbyname(A);
    if(user == null)
      return "loginfail";
    else if(!user.getPassword().equals(B))
      return "falsepaswd";
    else
      return "helloworld";

  }

public String hello( String username, String password, HttpSession session){
    session.setAttribute("a", username);
    session.setAttribute("b", password);
    user user = userService.findbyname(username);
    if(user == null)
      return "loginfail";
    else if(!user.getPassword().equals(password))
      return "falsepaswd";
    else
      return "helloworld";

  }

public String hello( HttpServletRequest req, HttpSession session){
    username=req.getParameter("username");
    password=req.getParameter("password");
    session.setAttribute("a", username);
    session.setAttribute("b", password);
    user user = userService.findbyname(username);
    if(user == null)
      return "loginfail";
    else if(!user.getPassword().equals(password))
      return "falsepaswd";
    else
      return "helloworld";

  }